1. Technical Field
The invention relates to detecting and tracking moving objects in a computer environment. More particularly, the invention relates to tracking translational and rotational movements of an object in a computer environment.
2. Description of the Prior Art
A variety of systems exist for tracking movements of objects. These systems track anywhere from a single dimension up to six dimensions. Some are specific for translations of objects in the three dimensions of a Cartesian coordinate system, while others track rotations of objects. There are also a variety of uses for these systems, ranging from motion tracking for animation production to controlling the movements of a cursor on a computer screen.
Many systems are available that track object movement by detecting the location of the object at frequent intervals and calculating the object""s motion as a sequence of location changes. The types of devices used for object location tracking include electromagnetic, acoustic, image-based, and optical systems.
Electromagnetic systems utilize transmitters than generate three orthogonal electromagnetic fields and detectors that include three orthogonal coils. Acoustic systems measure the time-of-flight of an acoustic wave from one or more transmitters to three or more detectors. Image-based systems utilize images from cameras that are then processed in a computer to locate specified objects.
Optical tracking systems usually use one of two main principles. One principle involves a scanned light source. Under these conditions, the timing for detection of the scanned source is used to determine the position of the light source. Other systems use multiple detectors that simultaneously monitor a continuous or flashed light source. These systems tend to be very expensive and many are limited in the number of dimensions that can be tracked.
Systems are also available that track object movement independently from the object""s location. Inertial systems are available that utilize accelerometers or gravitational field sensors. Gyroscopic devices are also available for detecting object motion but tend to be both large and inaccurate. These systems are also limited in the number of dimensions that can be tracked.
The computer mouse is the most widely used movement tracking device. Most computer mice can only track movement in two dimensions of translation. U.S. Pat. No. 5,393,970 describes a location tracking device that uses methods to track object location. However, this approach does not track rotations or reflections of light sources.
Some systems have been developed to track additional dimensions by including an accelerometer or gyroscope. Trackballs, joysticks and digitizing pads are also used for monitoring movements. Each of these devices has the limitation of only being able to monitor two dimensions at a time.
Other systems cannot measure rotational movement such as U.S. Pat. No. 5,892,501 which describes a wireless pointing device for cursor movement. This device uses a combination of ultrasonic and optical tracking components and does not measure rotational movement.
It would be advantageous to provide a spatial tracking system that provides an inexpensive system that monitors up to six dimensions at a time. It would further be advantageous to provide a spatial tracking system that does not require cabling between emitter and detector systems and is adaptable to a wide range of uses.
The invention provides a spatial tracking system. The system provides an inexpensive device that monitors up to six dimensions at a time. In addition, the invention does not require cabling between emitter and detector systems and is adaptable to a wide range of uses.
A preferred embodiment of the invention tracks movements of sources of radiated energy. In one embodiment of the invention, three sensor sets are included. Each sensor set includes a pair of sensors. Movements of a single radiation source with a radially symmetric emission pattern is tracked in up to six dimensions; X, Y, Z, yaw, pitch and radiation intensity. The invention is very useful for tracking over a limited spatial range and can be used to produce low-cost movement tracking systems.
Movements of more than one radiation source can be tracked by the invention. One method to track more than one radiation source is to have only one source active at any time. Another method is to have the different radiation sources turn on and off at different frequencies and employ methods that distinguish which sources are active at any time.
Sources with different radiation ranges or types are tracked at the same time using sensors tuned to the different radiation ranges or types. The ability to track more than one radiation source is useful for tracking multiple objects, multiple parts of an object, or multiple body parts.
The sensor sets may include more than two sensors. Increasing the number of sensors within a set increases the spatial range monitored and increases tracking accuracy. These sets optionally include sensors tuned to different radiation sources, such as light of different wavelengths. Two or more sensors are typically included for each type of energy source being tracked.
Other embodiments of the invention include more than three sensor sets. Increasing the number of sensor sets significantly increases the spatial range for the tracking system. This is particularly useful when tracking objects or people over large areas. It is also useful for tracking different parts of the body. Increasing the number of sensor sets also improves system accuracy. The different sensor sets could also include sensors tuned to different energy sources.
Individual sensors can be included together with the sensor sets and are useful for increasing the rotational range of the system beyond the range for translation tracking. Individual sensors provide background information or information from different radiation sources than those being tracked by the accompanying system.
Other aspects and advantages of the invention will become apparent from the following detailed description in combination with the accompanying drawings, illustrating, by way of example, the principles of the invention.